Backfunctionalized imidazolinium salts and nhc carbene-metal complexes

ABSTRACT

Backfunctionalized imidazolinium salts and methods of synthesizing the same and NHC carbene-metal complexes therefrom. For backfunctionalized imidazolinium salts of the formula: 
     
       
         
         
             
             
         
       
     
     Wherein R 1  is selected from the group consisting of an ester group, an amide group, and an aromatic group; R 2  is selected from the group consisting of hydrogen, an ester group, an amide group, and an aromatic group; R 3  and R 4  are each an aliphatic group; and
 
X is an anion; the method comprises cyclization of a halogenated acrylate with Hünig&#39;s base in a solvent.

Pursuant to 37 C.F.R. § 1.78(a)(4), this application is a continuationof U.S. application Ser. No. 16/103,267, filed Aug. 14, 2018, which wasa divisional of U.S. application Ser. No. 14/880,147, filed Oct. 9,2015, which claimed the benefit of and priority to ProvisionalApplication Ser. No. 62/062,069, filed 9 Oct. 2014. The disclosure ofeach of these applications is expressly incorporated herein byreference, each in its entirety.

RIGHTS OF THE GOVERNMENT

The invention described herein may be manufactured and used by or forthe Government of the United States for all governmental purposeswithout the payment of any royalty.

FIELD OF THE INVENTION

The present invention relates generally to inorganic carbene complexesand, more particularly, to backfluorinated N-heterocyclic carbene metalcomplexes.

BACKGROUND OF THE INVENTION

Chemical vapor deposition (hereafter, “CVD”) is a conventionally usedprocess for producing high-purity, high-performance materials, such asthin films on semiconductors or growing crystalline structures.Deposition of the films includes exposing a substrate to volatilechemicals, i.e., precursors, which react and/or decompose at a surfaceof the substrate.

The use of CVD for metal deposition, e.g., organometallic CVD or MOCVD,includes a metal atom (for example, but not limited to, Mo, Ta, Ti, W,Ru, Cu, Pt, and Pd) bonded to organic ligands. However, the CVD processhas limitations in that internal structures or surfaces, with tortuousfeatures, are not effectively coated.

Supercritical chemical fluid deposition (hereafter, “SFD”) is oneconventional solution that is capable of depositing a metal coating ontoa complicated surface/feature structure. During a SFD process, asupercritical fluid (substances at a temperature and pressure above acritical point (in a phase diagram) such that distinct gas and liquidphases do not exist), also referred to as the working fluid, is used asa solvent to the organometallic precursor. There are many supercriticalfluids available for SFD process, but the most convenient may be carbondioxide. The liquid-like state of the supercritical fluid enablesincreased solubility of the organometallic precursor, and the gas-likestate of the supercritical fluid enables a deep, conformal penetrationof the features of the substrate.

SFD processes have conventionally been performed in a hot-wallprocessing system 10, an example of which is shown in FIG. 1. Thehot-wall processing system 10 includes a processing chamber 12 enclosinga processing space 14 that is heated externally. A substrate 16 and anorganometallic precursor 18 are added to the processing chamber 12 andsealed. A working fluid (represented by arrows 20) is added, forexample, via an injection system 22, and the processing space 14 isheated until the temperature and pressure required for the supercriticalstate of the working fluid is exceeded. The organometallic precursor 18dissolves in the supercritical working fluid within the process space14. A reducing agent, usually hydrogen, is then introduced to cause themetal portion of the organometallic precursor 18 to deposit onto thesubstrate 16. However, the metal portion is also deposited on other,interior surfaces of the processing chamber 12.

While the hot-wall processing system 10 of FIG. 1 is effective atcoating substrates 16, the process is wasteful in that it deposits metalon all surfaces within the processing chamber 12. An alternative to thehot-wall processing system 10 is a cold-wall processing system 30, whichis shown in shown in FIG. 2. The cold-wall processing system 30 places asubstrate 32 on a heated pedestal 34 within the processing space 36 ofthe processing chamber 38. With the substrate 32 and an organometallicprecursor 40 in place, the processing chamber 38 is sealed andevacuated. A working fluid (represented by arrows 42) is added, forexample, via an injection system 44, and the processing chamber 38 isheated until the supercritical state of the working fluid is surpassed.The organometallic precursor 40 dissolves in the supercritical workingfluid, and then the reducing agent (again, usually hydrogen) is added.To prevent deposition of the metal component onto all interior surfacesof the chamber 38 (like the aforementioned hot-wall processing system 10(FIG. 1)), the organometallic precursor 40 should be thermally stable,stable to hydrogen reduction at lower temperature, and yet able to bereduced at elevated temperatures. The pedestal 34 of the cold-wallprocessing system 30 is heated such that deposition of the metallicportion is on the substrate and pedestal. Thus, the cold-wall processingsystem is more efficient than the hot-wall process 10 (FIG. 1), and isparticularly useful for depositing copper and ruthenium coatings.

Backfluorinated NHC carbene complexes, such as those having beendescribed in U.S. application Ser. No. 13/927,295 (being incorporatedherein by reference, in its entirety) have proven useful in overcomingthe foregoing issues with respect to the deposition of noble metals;however, the need for improvement remains. Particularly, there remains aneed for more efficient synthesis methods by which bulk quantities ofbackfluorinated NHC carbene complexes may be prepared for industrialuse. Moreover, there remains a need for mechanisms of synthesis thatenable additional functionalization of the NHC carbene complexes.

SUMMARY OF THE INVENTION

The present invention overcomes the foregoing problems and othershortcomings, drawbacks, and challenges associated with the synthesis ofNHC carbene complexes. While the invention will be described inconnection with certain embodiments, it will be understood that theinvention is not limited to these embodiments. To the contrary, thisinvention includes all alternatives, modifications, and equivalents asmay be included within the spirit and scope of the present invention.

According to one embodiment of the present invention a method ofsynthesizing a backfunctionalized imidazolinium salt comprises theformula:

In the formula, R¹ is selected from the group consisting of an estergroup, an amide group, and an aromatic group; R² is selected from thegroup consisting of hydrogen, an ester group, an amide group, and anaromatic group; R³ and R⁴ are each an aliphatic group; andX is an anion. The method comprises cyclization of a halogenatedacrylate with Hünig's base in a solvent.

In accordance with other embodiments of the present invention, a methodof synthesizing a backfunctionalized imidazolinium salt comprisescyclization of a halogenated acrylate with Hünig's base in a solvent.

Still other embodiments of the present invention are directed tobackfunctionalized imidazolinium salts comprising the formula:

In the formula, R¹ is selected from the group consisting of an estergroup, an amide group, and an aromatic group; R² is selected from thegroup consisting of hydrogen, an ester group, an amide group, and anaromatic group; R³ and R⁴ are each an aliphatic group; andX is an anion.

According to other embodiments of the present invention, abackfunctionalized imidazolinium salt comprises the formula:

In the formula, R¹ is selected from the group consisting of an estergroup, an amide group, and an aromatic group; R² is selected from thegroup consisting of hydrogen, an ester group, an amide group, and anaromatic group; each of R³ and R⁴ being separately selected from thegroup consisting of a C₁-C₂₀ alkyl group, C₁-C₂₀ partially fluorinatedalkyl group, an aryl group, an aryl group with para CF₃ functionality,an aryl group having C₁-C₂₀ partially fluorinated alkyl groups orpartially fluorinated alkoxy groups, and a C₁-C₂₀ partially fluorinatedaliphatic group, and a C₁-C₂₀ aryl group; and X is an anion.

In still other embodiments of the present invention, abackfunctionalized imidazolinium salt selected from the group offormulae consisting of:

In the formula, R¹ is selected from the group consisting of an estergroup, an amide group, and an aromatic group; R² is selected from thegroup consisting of hydrogen, an ester group, an amide group, and anaromatic group; each of R³ and R⁴ being separately selected from thegroup consisting of a C₁-C₂₀ alkyl group, C₁-C₂₀ partially fluorinatedalkyl group, an aryl group, an aryl group with para CF₃ functionality,an aryl group having C₁-C₂₀ partially fluorinated alkyl groups orpartially fluorinated alkoxy groups, and a C₁-C₂₀ partially fluorinatedaliphatic group, and a C₁-C₂₀ aryl group; each of R⁵ and R⁶ beingseparately selected from the group consisting of a partially fluorinatedalkyl group, a fluorinated aryl group, an aliphatic group, and an arylgroup; and X is an anion.

Still other embodiments of the present invention are directed tobackfunctionalized imidazolinium salt selected from the group offormulae consisting of:

In the formula, each of R³ and R⁴ being separately selected from thegroup consisting of a C₁-C₂₀ fluorinated alkyl group, a C₁-C₂₀fluorinated aryl group, a C₁-C₂₀ fluorinated aliphatic group, and aC₁-C₂₀ aryl group; and X is an anion.

Yet other embodiments of the present invention are directed to ionicliquids of the formula:

In the formula, R is a hydrogen or a methyl group; R′ is selected fromthe group consisting of hydrogen, an ester group, an amide group, and anaromatic group; R″ is selected from the group consisting of an alkylgroup and an aromatic group; the subscript m may range from 0 to 10; thesubscript n may range from 0 to 10; X is a halide or an anion; and Y isoxygen, sulfur, or NR″.

According to embodiments of the present invention, a method ofsynthesizing a backfluorinated imidazolinium salt includes cyclizationof a halogenated, fluorinated allyl ether with Hünig's base in polaraprotic solvent.

Other embodiments of the present invention are directed to methods ofsynthesizing backfluorinated second generation Grubbs' andGrubbs-Hoveyda catalysts. The methods include reacting a backfluorinatedNHC carbene with a first generation Grubbs' and Grubbs-Hoveyda catalyst.

Additional objects, advantages, and novel features of the invention willbe set forth in part in the description which follows, and in part willbecome apparent to those skilled in the art upon examination of thefollowing or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and attained by means ofthe instrumentalities and combinations particularly pointed out in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the presentinvention and, together with a general description of the inventiongiven above, and the detailed description of the embodiments givenbelow, serve to explain the principles of the present invention.

FIG. 1 is a schematic representation of a conventional, hot-wallprocessing system suitable for supercritical chemical fluid depositionprocesses.

FIG. 2 is a schematic representation of a conventional, cold-wallprocessing system suitable for supercritical chemical fluid depositionprocesses.

FIG. 3 is an illustrative representation of a formamidine cyclization ofhalogenated tetrafluoropropyl allyl ether in diglyme in the presence offormamidine base and according to an embodiment of the presentinvention.

FIG. 4 is an illustrative representation of a formamidine cyclization ofhalogenated tetrafluoropropyl allyl ether in diglyme in the presence ofN,N-diisopropylethylamine base according to another embodiment of thepresent invention.

FIG. 5 is an illustrative representation of formamidine cyclization of ahalogenated, fluorinated acrylate in toluene in the presence of Hünig'sbase and according to an embodiment of the present invention is shown.

FIG. 6 is an illustrative representation of formamidine cyclization of ahalogenated maleate in toluene in the presence of Hünig's base and inaccordance with an embodiment of the present invention.

FIG. 7 is an illustrative representation ionic liquid according to anembodiment of the present invention.

FIG. 8 is representation of 2-ethylhexyl imidazolinium salt, an ionicliquid according to an embodiment of the present invention.

FIG. 9 is an illustrative representation of formamidine cyclization of ahalogenated maleate in toluene in the presence of Hünig's base and inaccordance with an embodiment of the present invention.

FIGS. 10-13 are illustrative representations of backfunctionalized NHCcarbene-metal complexes in accordance with embodiments of the presentinvention.

FIG. 14 is an illustrative representation of the synthesis of abackfunctionalized NHC carbene complex in accordance with an embodimentof the present invention.

FIG. 15 is an illustrative representation of a backfunctionalized NHCcarbene-metal complex in accordance with another embodiment of thepresent invention.

FIG. 16 is a flowchart illustrating a method of depositing metal on asubstrate by cold wall supercritical chemical fluid deposition inaccordance with an embodiment of the present invention.

FIGS. 17A and 17B are illustrative representations oftransesterification and/or transamination of backfunctionalizedimidazolinium salts according to embodiments of the present invention.

FIGS. 18A-19B are exemplary, illustrative representations forsynthesizing Sticky-Cat catalyst-type systems (FIGS. 18A and 18B) andAquaMet catalyst-type systems (FIGS. 19A and 19B) in accordance withembodiments of the present invention.

FIGS. 20 and 21 are exemplary, illustrative representations of methodsof synthesizing silica-supported, backfunctionalized NHC carbene-metalcomplexes in accordance with two embodiments of the present invention.

It should be understood that the appended drawings are not necessarilyto scale, presenting a somewhat simplified representation of variousfeatures illustrative of the basic principles of the invention. Thespecific design features of the sequence of operations as disclosedherein, including, for example, specific dimensions, orientations,locations, and shapes of various illustrated components, will bedetermined in part by the particular intended application and useenvironment. Certain features of the illustrated embodiments have beenenlarged or distorted relative to others to facilitate visualization andclear understanding. In particular, thin features may be thickened, forexample, for clarity or illustration.

DETAILED DESCRIPTION OF THE INVENTION

Backfunctionalized imidazolinium salts according to embodiments of thepresent invention include a general structure of:

(hereafter referred to as “backfunctionalized imidazolinium”) wherein R¹is selected from the group consisting of an ester group, an amide group,and an aromatic group, R² is selected from the group consisting ofhydrogen, an ester group, an amide group, and an aromatic group, and R³and R⁴ are each separately selected from the group consisting a C₁-C₂₀alkyl group, C₁-C₂₀ partially fluorinated alkyl group, an aryl group, anaryl group with para CF₃ functionality, an aryl group having C₁-C₂₀partially fluorinated alkyl groups or partially fluorinated alkyoxygroups, and a C₁-C₂₀ partially fluorinated aliphatic group, and a C₁-C₂₀aryl group (with the proviso that some partially fluorinated alkylgroups may require longer buffer). X, in the illustrated structure, is ahalogen. Functional groups of R¹ and R² may be in either a cis- ortrans-configuration, as provided in greater detail below.

As used herein, “partially fluorinated” is a perfluoroalkyl group havinga 1-3 carbon methylene buffer attached by either a carbon[perfluoroctyl(ethyl)-] or an oxygen [perfluoroctyl(ethoxy)-] to anaromatic ring.

As used herein, “olefin metathesis” is an organic reaction in whichfragments of alkenes are redistributed by scission and regeneration ofcarbon-carbon double bonds.

As used herein, “functionalized” refers to an ester, amide, or aromaticfunctionality.

“Backfunctionalized” refers to an ester, amide, or aromaticfunctionality that is attached to the 4 position, 5 position, or both ofthe imidazolinium ring.

According to more specific embodiments of the present invention,backfunctionalized imidazolinium salts may be selected from the group ofstructures consisting of:

where R¹, R², R³, R⁴, and X are as described above and R⁵ and R⁶ areeach separately selected from a fluorinated alkyl group, a fluorinatedaryl group, an aliphatic group, and an aryl group. The mono- anddi-ester embodiments may be extremely versatile and, as one of ordinaryskill in the art having the benefit of this disclosure would appreciate,could accommodate a wide variety of functional groups at R¹-R⁴.

Still further embodiments of the present invention includebackfunctionalized imidazolinium salts selected from the groupconsisting of:

Backfunctionalized NHC carbenes according to embodiments of the presentinvention may be coordinated in metal complexes, wherein the metal isselected from the group consisting of rhenium, ruthenium, osmium,rhodium, iridium, palladium, platinum, silver, and gold. Furthermore,inorganic complexes for coordination with backfunctionalized NHCcarbenes according to embodiments of the present invention may includeacetylacetonate, alkoxy, alkyl, aryl, aryloxy, carbonyl, halide, imido,oxo, pyridine, trialkylphosphine, and triarylphosphine.

Referring now to the figures, and in particular to FIG. 3, synthesis ofbackfluorinated N-heterocyclic (“NHC”) carbenes, and more particularlysynthesis of backfluorinated imidazolinium salts which may bedeprotonated to form free backfunctionalized NHC carbenes, according toan embodiment of the present invention is shown. Generally, synthesisincludes formamidine cyclization in a polar aprotic solvent. Suitablepolar aprotic solvents may include, but are not limited to ethyleneglycol dimethyl ether (glyme), diethylene glycol dimethyl ether(diglyme), and triethylene glycol dimethyl ether (triglyme). In theparticularly illustrative embodiment of FIG. 3, formamidine cyclizationof brominated tetrafluoropropyl allyl ether and mesityl formamidine indiglyme (the selected polar aprotic solvent) in the presence of mesitylformamidine as the base is shown.

A similar embodiment of formamidine cyclization is shown in FIG. 4, butuses N,N-diisopropylethylamine (commonly referred to as “Hünig's base”)as the base.

Referring now to FIG. 5, formamidine cyclization of a halogenated,fluorinated acrylate (specifically illustrated as tetrafluoropropylacrylate) is shown in accordance with an embodiment of the presentinvention. Although not necessary, the halogenated, fluorinated acrylatemay first be synthesized from a fluorinated acrylate, which is alsoincluded in the illustration of FIG. 5. A variety of fluorinatedacrylates, such as perfluorooctyl-ethyl acrylate, and higher homologsbased on tetrafluoropropanol, such as 1H,1H,9H-perfluorononanol mayadditionally or alternatively be used. Various aliphatic and aromaticesters and amides may additionally or alternatively be used. Formamidinecyclization according to this embodiment, carried out in toluene in thepresence of Hünig's base, is an exothermic reaction and does not requireheating. Still other bases may be used in synthesis of imidazoliniumsalts according to embodiments of the present invention, such astriethylamine and pyridine, may be used. It is believed thatconventional methods have been unsuccessful in using such bases becausethe elevated temperatures required to complete the cyclization(temperatures in excess of 100° C.). Such bases are too nucleophilic atelevated temperatures and thus the less nucleophilic Hünig's base oraromatic formamidine was used. Because the synthesis methods accordingto embodiments of the present invention occur at temperatures that arelower than the conventional methods, such alternative bases becomeviable options. Moreover, cost savings via these alternative bases mayincrease productivity while minimizing costs.

In still other embodiments, such as the embodiment shown in FIG. 6,formamidine cyclization of a halogenated maleate (specificallyillustrated as brominated dimethyl maleate) may be carried out intoluene in the presence of Hünig's base at low heat (temperatures beingless than about 60° C.). While not wishing to be bound by theory, it isbelieved that formamidine cyclization proceeds firstly, by a standardbromination mechanism where bromine attacks the double bond and formscyclic bromonium cation. The resulting bromide anion attacks one of thecarbons from the back resulting in the d,l dibromide.

While not specifically illustrated, embodiments of formamidinecyclization of other olefin based ester compounds (such as fumarate) mayproceed in manner similar to those embodiments illustrated in FIGS. 5and 6; however, it may be necessary, in such embodiments, to furtherheat the reaction during cyclization because of steric hindrance.

Besides the mesityl formamidine complex, as shown herein, additionalformamidine complexes are possible according to other embodiments.Generally, such embodiments may include, but are not limited to aromaticformamidine complexes (such as, o-tolyl-formamidine,p-tolyl-formamidine, and 2,6-diisopropylphenyl-formamidine), fluorinatedformamidine complexes (such as, 4-CF₃-phenyl-formamidine) and aliphaticformamidine complexes (such as, adamantyl-formamidine,cyclohexyl-formamidine, and 2-ethyl-1-hexyl-formamidine). Suchimidazolinium salts may be synthesized using a solvent (such as tolueneor acetone) with a base (such as Hünig's base, triethylamine, or, insome embodiments, formamidine) with moderate heating (less than about60° C., or more preferably, about 40° C.) for a period of time (lessthan about 12 hours, or more preferably, about 4 hours); however, thetemperature, reaction time, or both may depend on an amount of sterichindrance (such as in reactions using adamantyl-formamidine and2,6-diisopropylphenyl-formamidine).

These embodiments of the present invention demonstrate a significantbenefit over conventional synthesis methods, which were traditionallylimited to aromatic side chains (R³ and R⁴ groups) and such methods notnecessarily applied to aliphatic groups.

Synthesis methods, as described herein, may in some embodiments yield anew class of imidazolinium salts that behave as ionic liquids. FIG. 7illustrates, generally, a structure for such an ionic liquid, whereinsubscripts m and n may each range from 0 to 10 and the subscript m isselected independently of the subscript n. X in FIG. 7 may be a halideor another anion; R may be hydrogen or a methyl group; R′ may behydrogen, an ester group, or an amide group; R″ may be an alkyl group oran aromatic group; Y may be oxygen, sulfur, or NR″. Ionic liquids aresalts that have a melting point of less than about 100° C. Oneparticular species of ionic liquid prepared in accordance withembodiments of the present invention is shown in FIG. 8 (2-ethylhexylimidazolinium salt), and was synthesized by cyclization of 2-ethylhexylformamidine and methyl 2,3-dibromopropionate (brominated methylacrylate) using either Hünig's base or triethylamine as the base. The2-ethylhexyl imidazolinium ionic liquid of FIG. 8 was soluble in anon-polar solvent (toluene) and is viscous oil at room temperature.

Ionic liquids, as described herein, may be useful as a plasticizer foradvanced propellant formulations. Suitable propellant formulations mayinclude, but are not limited to, ammonium perchorate-based propellants,ammonium dinitramide-based propellants, and furazan-based propellants.In accordance with other embodiments, the ionic liquids may be supportedonto a surface such that two chains are extending away from theimidazolinium salt and approximately parallel to said surface.

Given the benefit of the disclosure herein, the skilled chemist wouldappreciated that formation of ionic liquids by cyclization according toembodiments of the present invention may include Hünig's base or otherones or combinations of bases as are provided herein.

One of the difficulties of conventional carbenes is the insolubility inscCO₂ at lower pressures (less than about 3000 PSI). Whilemonofunctional imidazolinium salts, as prepared in accordance withembodiments discussed above, are potentially capable of supporting aperfluoroalkyl group with 24 fluorines (H(CF₂)₁₂CH₂O⁻), economicallyspeaking, only 16 or 17 fluorines (H(CF₂)₈CH₂O⁻ and (F(CF₂)₈CH₂CH₂O⁻)are feasible. An alternative would be to functionalize sides groups ofthe imidazolinium; however, such an option may present electronic risks.Alternatively still, functional groups could be added to a backside ofthe imidazolinium ring. In that regard, functionalization would lead toeither performing a transamination (two perfluoroalkyl chains on theamine) or adding another ester linkage to the back of the ring. Adding asecond ester group to the back of the ring is the more economical of thetwo choices.

In referring again to FIG. 6, and again, while not wishing to be boundby theory, it is believed the cyclization reaction includes a mesoproduct of a soluble halogen ion (rendered soluble by the Hünig's basecation), which displaces one of the halogens of the succinate. Heatingthe reaction at 60° C. for an extended period of time resulted in theobserved meso product. The possibility of isomerization result may bereduced by limiting soluble halogens, which may be accomplished by theuse of triethylamine and proceeding at a reduced temperature (forexample, 40° C.). The resulting mechanism is shown in FIG. 9 and yieldsonly one observed isomer.

Backfunctionalized imidazolinium salts according to embodiments of thepresent invention are not easily deprotonated the 2-proton by strongbases (such as potassium bis(trimethylsilyl)amide (“KHMDS”) or potassiumhydroxide) to yield a free NHC carbene for attachment to a metal center.Instead, to obtain a metal complex with the backfunctionalizedimidazolinium salts described herein, such salts may be reacted with theimidazolinium salt with silver oxide to yield an NHC carbene/silverhalide complex. This complex was then subsequently reacted with a metalcomplex to afford the NHC carbene/metal complex.

Using this method, embodiments of the backfunctionalized imidazoliniumsalts according to the present invention may be attached to a metalcenter, M, via first and second ligands, L¹ and L³. Additional ligands,L², L³ (if not NHC), and L⁴ may be used to attach the metal center toyield a backfluorinated NHC carbene-metal complex. The third ligand, L²(or L³) may be selected from the group consisting of an acetylacetonate,alkoxy, alkyl, aryl, aryloxy, carbonyl, halide, imido, oxo, pyridine,trialkylphosphine, or triarylphosphine; and the fourth ligand, L⁴, maybe selected from the group consisting of an acetylacetonate, alkoxy,alkyl, aryl, aryloxy, carbonyl, halide, imido, oxo, pyridine,trialkylphosphine, or triarylphosphine.

With reference now to FIGS. 10-13, four arrangements of the metalcomplex are shown. Generally, selection of the metal may depend on aparticular application or use of the inorganic backfluorinated NHCcarbene-metal complex. For example, in supercritical fluid deposition, Mmay be selected from the group consisting of rhenium, ruthenium, osmium,rhodium, iridium, palladium, platinum, silver, and gold; in catalysisprocesses, M may be selected from the group consisting of rhenium,ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium,platinum, copper, silver, and gold. More particularly, the metal of FIG.10 may be selected from the group consisting of cobalt, iridium, andrhodium; the metal of FIG. 11 may be selected from the group consistingof nickel, palladium, and platinum; the metal of FIG. 12 may be selectedfrom the group consisting of copper, silver, and gold; and the metal ofFIG. 13 may be selected from the group consisting of rhenium, ruthenium,osmium, cobalt, rhodium, iridium, nickel, palladium, and platinum.

Coordination of the metal to the carbene may be accomplished by adding asilver-NHC carbene complex to chloro-cyclooctadiene-iridium dimer, thelatter of which is shown in FIG. 14.

FIG. 15 illustrates ruthenium alkylidene system, which may be preparedin accordance with the method described herein by the addition of asilver-NHC carbene complex to the first Generation Grubbs orGrubbs-Hoveyda ruthenium alkylidene catalyst.

Reaction of conventional, backfluorinated NHC carbenes with firstgeneration Grubbs' and Grubbs-Hoveyda catalyst gave backfluorinatedsecond generation Grubbs' and Grubbs-Hoveyda catalysts. These catalystswere active for olefin metathesis and ring opening metathesispolymerization.

Imidazolinium salts, according to the various embodiments herein, may beused for a number of applications. For instance, such salts areespecially suited for use as SCFD precursors. In the case of noblemetals, the purpose of the backfluorinated NHC carbene-metal complexderived from the imidazolinium salts describe herein is to render themetal precursor soluble in supercritical solvent and stable to hydrogenat lower temperatures, and to be removed and deposit the metal onto thesubstrate at elevated temperatures.

The details of SCFD are provided in U.S. application Ser. No.13/927,295; however, and briefly with reference now to FIGS. 2 and 16, amethod of depositing metals using supercritical fluid deposition methodsis described in accordance with one embodiment of the present invention.In using the cold-wall processing system 30 of FIG. 2, a noble metal maybe deposited using SFD processing conditions according to an embodimentof the present invention illustrated in the flowchart of FIG. 16;however, the skilled artisan will readily appreciate that theillustrated cold wall reactor 30 layout should not be considered to belimiting. In the instant embodiment, the organometallic precursor 40comprises a backfluorinated NHC carbene-metal complex according to atleast one embodiment of the present invention.

In Block 50 of FIG. 16, a precursor 22 comprising a backfluorinated NHCcarbene-metal complex, optionally with a cosolvent, is placed in theprocessing space 36. The substrate 32 is positioned on the substrateholder 34 (Block 52) and the processing space 36 is sealed and evacuated(Block 54).

A supercritical solvent, for example, carbon dioxide, may be injectedvia the injection system 44 and the chamber wall 38 may, optionally, beheated (Block 56). The reactor temperature depends on the selectedsupercritical solvent but, for exemplary purposes, may be 60° C. forcarbon dioxide.

Once a supercritical state is achieved (“Yes” branch of Decision Block58), the backfluorinated NHC carbene-metal complex precursor 40 beginsto dissolve into the supercritical solvent, and a reducing agent may beinjected via the injection system 44 (Block 60). Otherwise (“No” branchof Decision Block 58), the injection (Block 56) continues.

With the backfluorinated NHC carbene-metal complex precursor 40dissolved, the substrate holder 34 may be heated to a desiredtemperature (Block 62). Because the substrate holder 34, and ultimatelythe substrate 32 are at an elevated temperature, deposition of the metalportion of the backfluorinated NHC carbene-metal complex precursor 40from the supercritical solvent onto the substrate 32 may occur withoutdeposition of metal portion onto chamber walls 38 or other components ofthe system 30.

With deposition complete, the system 30 may be cooled, the pressurerelieved, and the substrate 32 removed.

According to another embodiment of use, the functional groups of suchimidazolinium salts may be modified using transesterification. Whilealcohols are a primary group of interest, amines and sulfides may alsobe used to displace the ester group. Moreover, such methods oftransesterification may be used for additional systems, described indetail below.

With reference now to FIGS. 17A and 17B, transesterification and/ortransamination of backfunctionalized imidazolinium salts, according tothe present invention, may afford catalysts that are conventionallydifficult to manufacture. While the exemplary imidazolinium saltsillustrated in FIGS. 17A and 17B are shown to include mesityl R³ and R⁴groups, it would be readily appreciated by those of ordinary skill inthe art having the benefit of the disclosure herein that other groupsmade be used. More particularly, three illustrative embodiments havingfluorocarbon (pathway β of FIG. 17B), long chain hydrocarbon (pathway αof FIG. 17B), and allyl (pathway γ of FIG. 17B) backfunctionalizedgroups (R¹ with R²=H) synthesized by an addition of the Grignard reagentto a diimine and reduction and cyclization to yield the imidazoliniumsalt. Such reactions may be carried out on a large scale with theproviso that the Grignard addition and the reduction steps are performedwith care on larger scale.

According to one exemplary embodiment, water soluble systems may besynthesized using the methods described herein by thetransesterification of methyl ester imidazolinium salt with polyethyleneglycol monomethyl ether. Conventionally, polyethylene glycol mesylate isadded to 2-3-dimesityl-1-propanol and the product purified by columnchromatography; however, such procedure is difficult to scale up.According to methods herein, the acid may be added and then cyclizedwith triethylorthoformate. In FIG. 18A, a “Sticky-cat” precursor issynthesized by bromination of N,N-dimethylamino-propene, followed by theaddition of mesistylamine/base, and then cyclization by the addition ofacid and triethylorthoformate cyclization. FIG. 19A illustrates analternative embodiment wherein an “AquaMet” precursor is synthesizedusing a similar mechanism but for brominating allyl-methyl-piperazine.In FIGS. 18B and 19B, alternative potential pathways usingtransesterification are shown.

With references now to FIGS. 20-21, and in accordance with otherembodiments of the present invention, the acrylate technology may beused for supported catalysts systems. For example, imidazolinium salts,as described herein, may, via transesterification, include a supportedsystem. A suitable support system may include triethoxysilane as ananchor.

FIG. 20 illustrates an exemplary embodiment where a supported secondGeneration Grubb-Hoveyda catalyst is prepared.

FIG. 21 illustrates another exemplary embodiment that does not requiresilver transmetallation step. This methodology takes advantage of thelack of access to the α-proton to the ester. When an imidazolinium saltis in solution and homogenous, the addition of a strong base maypreferentially deprotonate the α-proton while the 2-proton remainsintact. Still, the 2-proton may be deprotonated and then the carbene maydeprotonate the α-proton. In a supported system, access to the α-protonis limited to side access and any generated carbenes cannot deprotonatethe α-proton due to site isolation. A bulky base such as KHMDS will berequired.

While not particularly shown herein, backfluorinated NHC carbenes andbackfluorinated NHC carbene-metal complexes according to variousembodiment of the present invention may also be used within the field ofcatalysis. For example, backfluorinated NHC carbenes according tovarious embodiments of the present invention and as applied totransition metal catalyzed reactions afford new systems that are solublein fluorinated solvents while retaining catalytic activity. Moreparticularly, the disclosed backfluorinated NHC carbenes may be usefulin biphase fluorous catalysis, wherein efficiency of a chemical reactionis increased by placing the active species in a fluorinated phase.Reactants, in a nonfluorinated phase, migrate into the fluorinated phaseactive species such that a chemical transformation takes place. Thereactants may then migrate out of the fluorinated phase active species.Use of backfluorinated NHC carbene-metal complexes may increaseefficient separation of product from the catalyst, particularly insystem comprising fluorinated solvents or the reaction of olefins havinga fluoroalkyl group.

The following examples illustrate particular properties and advantagesof some of the embodiments of the present invention. Furthermore, theseare examples of reduction to practice of the present invention andconfirmation that the principles described in the present invention aretherefore valid but should not be construed as in any way limiting thescope of the invention.

Example A—Imidazolinium Compounds from Acrylate and Maleate Systems

A scintillation vial was charged with a stir bar, mesityl formamidine(2.00 g, 7.13 mmol), toluene (8 g) and the tetrafluoropropyl2,3-dibromopropionate (3.08 g, 8.92 mmol). The mixture is set stirringand a slight excess of Hünig's base (1.01 g, 7.84 mmol) is added. Thereaction is exothermic and the solution goes clear. After a few minutes,the product and Hünig's base hydrobromide precipitate from solution.After stirring overnight, this solid is collected by filtration andwashed with toluene. The solid is suspended in acetone and stirred foran hour. The remaining solid is isolated by filtration, washed withacetone and dried under vacuum. ¹H, ¹³C and ¹⁹F NMR, and massspectrometry are consistent with the expected product.

This reaction was remarkable in that the reaction occurred very quicklyupon addition of the Hünig's base. The other reported reactions wereheated above 100° C. to affect the cyclization.

Maleate (cis double bond) was chosen over fumarate (trans double bond)because the maleate functionality should result in a d,lbackfunctionalization. The reasoning behind this is due to an assumptionon how the formamidine cyclization proceeds. Firstly, the bromination ofthe maleate is thought to proceed through the standard brominationmechanism where bromine attacks the double bond and forms cyclicbromonium cation. The resulting bromide anion attacks one of the carbonsfrom the back resulting in the d,l dibromide. This is confirmed by NMRspectroscopy where only one isomer is present. Upon addition of themesityl formamidine and Hünig's base, the reaction did not occurspontaneously like the acrylate based system and some heating wasrequired. After a few hours at 60° C., a white solid was isolated byfiltration, suspended in acetone, filtered once again and dried.

¹H, ¹³C NMR and mass spectrometry suggest that the expected product wasformed although the data indicate a mixture of d,l and meso isomers wasformed. These results suggest that soluble bromide anion displaced oneof the bromides of the d,l dibromo maleate to give the meso dibromomaleate. Confirmation of this displacement includes an experimentwherein d,l dibromide and tetrabutylammonium bromide were heated at 60°C. for several hours (see FIG. 10). The starting d,l dibromo succinateand meso dibromo succinate were both observed.

Example B—Cyclization Specificity

Generally, a scintillation vial was charged with a stir bar, the targetformamidine (1.5 g, 1 equivalent), toluene (11 g to 16 g) and Hünig'sbase (1.2 equivalents). The mixture is set stirring and methyl2,3-dibromopropionate (1.2 equivalents) was added. The reaction isstirred at 40° C. for four hours. The solid was filtered and washed withtoluene. A sample of the solid was taken and analyzed by NMRspectroscopy. Successful reactions showed Hünig's base present and theresonance of the product with a distinct 2-H peak at about δ 11.4 andthe three 4,5-H peaks at about δ 6.21, 5.13, and 4.37 (4-CF₃-phenylentry). The exception was the formation of the 2-ethylhexylimidazolinium salt that is soluble in toluene. Unsuccessful reactionsshowed only Hünig's base as the solid.

Solids from the successful reactions were washed with acetone, suspendedin acetone/water and stirred for an hour. Remaining solid was isolatedby filtration, washed with acetone, and dried under vacuum.

¹H NMR spectroscopy in CDCl₃ exhibited characteristic resonances on amonobackfunctional imidazolinium salt (the distinct 2-H peak at about δ11.4 and the three 4,5-H peaks at about δ 6.21, 5.13, and 4.37.).

Results for the survey are summarized in Table 1, below.

TABLE 1 ALIPHATIC PRECURSOR PRODUCT ADDITIONAL NOTE mesitylimidazolinium product o-tolyl- imidazolinium product p-tolyl-imidazolinium product 2,6-diisopropylphenyl- imidazolinium productcontained starting formamidine 4-CF₃-phenyl- imidazolinium product3-CF₃-phenyl- 2-CF₃-phenyl- 3,5-(CF₃)₂-phenyl- 2,4,6-trifluorophenylpentafluorophenyl adamantyl- imidazolinium product contained startingformamidine cyclohexyl- imidazolinium product2-ethyl-1-hexyl-formamidine imidazolinium product contained startingHünig's base, HBr; see Example D - Ionic Liquids

As shown, cyclization according to embodiments of the present inventionmay be used for both aromatic formamidines (conventionally common) andaliphatic formamidines.

Example C—Cyclization with Alternative Bases

Because Hünig's base may be economically prohibitive to bulk quantityproduction, a cyclization of mesityl formamidine with methyl2,3-dibromopropionate was carried out with triethylamine as the base.

A scintillation vial was charged with a stir bar, the mesitylformamidine (2.00 g, 7.13 mmol), toluene (14 g) and methyl2,3-dibromopropionate (2.19 g, 8.92 mmol). The mixture was set stirringand triethylamine (0.79 g, 7.85 mmol) was added. The reaction wasstirred at 40° C. for four hours. The solid was filtered and washed withtoluene and then acetone. The solid was then suspended in water andstirred for an hour. The solid was collected by filtration, washed withacetone, and dried.

The ¹H NMR spectrum of this product is identical to the product of theHünig's base reaction in Example B.

Example D—Ionic Liquids

Cyclization of 2-ethyl-1-hexyl formamidine, according to the methoddescribed in Example B, resulted in formation of a 2-ethylhexylimidazolinium salt. This particular product is soluble in toluene and isa viscous oil at room temperature.

A small amount of Hünig's base salt in the mixture that cannot be washedaway as the Hünig's base salt is slightly soluble in toluene. Thecyclization reaction was rerun using triethylamine as the base (notingthat the triethylamine salt is insoluble in toluene).

A round bottom flask was charged with a stir bar, the 2-ethylhexylformamidine (15.00 g, 55.87 mmol), toluene (75 g) and triethylamine(6.78 g, 67.04 mmol). The mixture was set stirring and methyl2,3-dibromopropionate (16.49 g, 67.04 mmol) was added. The reaction wasstirred at 40° C. for four hours. The mixture was cooled to roomtemperature and the solid was filtered and washed with toluene and setaside. The filtrate was evaporated at room temperature under vacuum andthen heated under vacuum for an hour at 60° C. to drive off anyunreacted materials. The liquid was cooled to yield a yellow, viscousoil at room temperature.

¹H NNMR exhibits the distinctive peaks of four different imidazolinium2-H protons centered at δ 10.05 and the three 4, 5 protons at δ 4.02,4.34, and 4.90.

A NEt₃.HBr free product was obtained. The base-free product is also anionic liquid.

The ¹H NMR spectrum of this product was quite complicated with fourdifferent 2-protons present. This phenomenon is due to the fact thatthere are three diastereotopic centers in the 2-ethylhexyl imidazoliniumsalt which should result in eight possible diastereomeric combinations,of which four are observable by ¹H NMR and the other four are NMRequivalent to the observed four. While the imidazolinium ring structureis present for all four observed diastereomers, the presence of theseeight molecules reduces the possibility of the order required forcrystallization. Addition of another stereocenter (planned) will resultin 16 different diastereomers.

Example E—Transesterification by Tetrafluoropropanol

A round bottomed flask was charged with a stir bar, toluene (8 g),methyl ester mesityl imidazolinium bromide (2.00 g, 4.49 mmol),tetrafluoropropanol (2.96 g, 22.45 mmol) and a catalytic amount ofp-toluenesulfonic acid. A distillation head was attached and suspensionwas heated at 60° C. under nitrogen for several hours. The reaction wascooled and the colorless solid filtered, washed with toluene, and driedunder vacuum. ¹H NMR shows starting material as well as thetetrafluoropropyl ester. The resonances are identical to the previouslyprepared tetrafluoropropyl ester mesityl imidazolinium bromide salt(Example A).

While the present invention has been illustrated by a description of oneor more embodiments thereof and while these embodiments have beendescribed in considerable detail, they are not intended to restrict orin any way limit the scope of the appended claims to such detail.Additional advantages and modifications will readily appear to thoseskilled in the art. The invention in its broader aspects is thereforenot limited to the specific details, representative apparatus andmethod, and illustrative examples shown and described. Accordingly,departures may be made from such details without departing from thescope of the general inventive concept.

What is claimed is:
 1. An ionic liquid having comprising the formula:

R being a hydrogen or a methyl group; R′ being selected from the groupconsisting of hydrogen, an ester group, an amide group, and an aromaticgroup; R″ being selected from the group consisting of an alkyl group andan aromatic group; the subscript m ranging from 0 to 10; the subscript nranging from 0 to 10; X being a halide or an anion; and Y being oxygen,sulfur, or NR″.
 2. The ionic liquid of claim 1, wherein the ionic liquidhas a chemical name of 2-ethylhexyl imidazolinium salt.
 3. A plasticizerfor a propellant formulation, the plasticizer comprising the ionicliquid of claim
 1. 4. The plasticizer of claim 3, wherein the propellantformulation further comprises: ammonium perchorate-based propellants. 5.The plasticizer of claim 3, wherein the propellant formulation furthercomprises: ammonium dinitramide-based propellants
 6. The plasticizer ofclaim 3, wherein the propellant formulation further comprises:furazan-based propellants
 7. A method of synthesizing a backfluorinatedimidazolinium salt, the method comprising: cyclization of a halogenated,fluorinated allyl ether with Hünig's base in polar aprotic solvent. 8.The method of claim 7, wherein the polar aprotic solvent is selectedfrom the group consisting of ethylene glycol dimethyl ether, diethyleneglycol dimethyl ether, and triethylene glycol dimethyl ether.
 9. Amethod of synthesizing backfluorinated second generation Grubbs' andGrubbs-Hoveyda catalysts, the method comprising: reacting abackfluorinated NHC carbene with a first generation Grubbs' andGrubbs-Hoveyda catalyst.
 10. The method of claim 9, wherein thebackfluorinated second generation Grubbs' and Grubbs-Hoveyda catalystsare active for olefin metathesis and ring opening metathesispolymerization.